As the title asked, what's the difference?
When should I use one or the other?
Also, anyone got a "canonical" definition of putty-256color's termcap/terminfo? Google had been less than helpful for searching that. Heck, Google had been less than helpful for ALL my questions in this Question!
There's a terminfo entry for putty-256color shipped with ncurses like the rest of the terminfo entries.
On Ubuntu 20.04 at least, terminfo entries are split between the ncurses-base (included by default) and ncurses-term (not). The putty-256color is in the latter.
When both are available (after installing ncurses-term on that version of Ubuntu at least), you'll be able to compare xterm-256color and putty-256color with infocmp.
You can also look at the source definition of those entries in misc/terminfo.src in the ncurses sources or online for the latest version (PuTTY section). In ncurses-6.2-20201107,
putty-256color|PuTTY 0.58 with xterm 256-colors,
use=xterm+256setaf, use=putty,
(though that 0.58 may be misleading as comments above the putty entry mention 0.71).
So you'll see it includes the base putty definition and the same sequences as xterm for 256 color.
Running infocmp -xL putty-256color xterm-256color with that version of ncurses, I get:
comparing putty-256color to xterm-256color.
comparing booleans.
auto_left_margin: T:F.
backspaces_with_bs: F:T.
can_change: F:T.
has_meta_key: F:T.
has_status_line: T:F.
no_pad_char: F:T.
prtr_silent: F:T.
xon_xoff: T:F.
AX: F:T.
comparing numbers.
columns: NULL, 80.
lines: NULL, 24.
no_color_video: 22, NULL.
U8: 1, NULL.
comparing strings.
acs_chars: '``aaffggjjkkllmmnnooppqqrrssttuuvvwwxxyyzz{{||}}~~', '``aaffggiijjkkllmmnnooppqqrrssttuuvvwwxxyyzz{{||}}~~'.
clear_margins: NULL, '\E[?69l'.
clear_screen: '\E[H\E[J', '\E[H\E[2J'.
cursor_down: '\ED', '\n'.
cursor_normal: '\E[?25h', '\E[?12l\E[?25h'.
cursor_up: '\EM', '\E[A'.
cursor_visible: NULL, '\E[?12;25h'.
dis_status_line: '\E]0;^G', NULL.
display_pc_char: '%?%p1%{8}%=%t\E%%G\342\227\230\E%%@%e%p1%{10}%=%t\E%%G\342\227\231\E%%@%e%p1%{12}%=%t\E%%G\342\231\0\E%%@%e%p1%{13}%=%t\E%%G\342\231\252\E%%@%e%p1%{14}%=%t\E%%G\342\231\253\E%%@%e%p1%{15}%=%t\E%%G\342\230\274\E%%@%e%p1%{27}%=%t\E%%G\342\206\220\E%%@%e%p1%{155}%=%t\E%%G\340\202\242\E%%@%e%p1%c%;', NULL.
ena_acs: '\E(B\E)0', NULL.
enter_alt_charset_mode: '^N', '\E(0'.
enter_ca_mode: '\E[?47h', '\E[?1049h\E[22;0;0t'.
enter_dim_mode: NULL, '\E[2m'.
enter_italics_mode: NULL, '\E[3m'.
enter_pc_charset_mode: '\E[11m', NULL.
enter_secure_mode: NULL, '\E[8m'.
exit_alt_charset_mode: '^O', '\E(B'.
exit_attribute_mode: '\E[m^O', '\E(B\E[m'.
exit_ca_mode: '\E[2J\E[?47l', '\E[?1049l\E[23;0;0t'.
exit_italics_mode: NULL, '\E[23m'.
exit_pc_charset_mode: '\E[10m', NULL.
from_status_line: '^G', NULL.
init_2string: '\E7\E[r\E[m\E[?7h\E[?1;4;6l\E[4l\E8\E>\E]R', '\E[\041p\E[?3;4l\E[4l\E>'.
initialize_color: NULL, '\E]4;%p1%d;rgb\072%p2%{255}%*%{1000}%/%2.2X/%p3%{255}%*%{1000}%/%2.2X/%p4%{255}%*%{1000}%/%2.2X\E\'.
key_a1: '\EOq', '\EOw'.
key_a3: '\EOs', '\EOy'.
key_b2: '\EOr', '\EOu'.
key_backspace: '\177', '^H'.
key_c1: '\EOp', '\EOq'.
key_c3: '\EOn', '\EOs'.
key_end: '\E[4~', '\EOF'.
key_f0: '\EOy', NULL.
key_f1: '\E[11~', '\EOP'.
key_f13: '\E[25~', '\E[1;2P'.
key_f14: '\E[26~', '\E[1;2Q'.
key_f15: '\E[28~', '\E[1;2R'.
key_f16: '\E[29~', '\E[1;2S'.
key_f17: '\E[31~', '\E[15;2~'.
key_f18: '\E[32~', '\E[17;2~'.
key_f19: '\E[33~', '\E[18;2~'.
key_f2: '\E[12~', '\EOQ'.
key_f20: '\E[34~', '\E[19;2~'.
key_f21: NULL, '\E[20;2~'.
key_f22: NULL, '\E[21;2~'.
key_f23: NULL, '\E[23;2~'.
key_f24: NULL, '\E[24;2~'.
key_f25: NULL, '\E[1;5P'.
key_f26: NULL, '\E[1;5Q'.
key_f27: NULL, '\E[1;5R'.
key_f28: NULL, '\E[1;5S'.
key_f29: NULL, '\E[15;5~'.
key_f3: '\E[13~', '\EOR'.
key_f30: NULL, '\E[17;5~'.
key_f31: NULL, '\E[18;5~'.
key_f32: NULL, '\E[19;5~'.
key_f33: NULL, '\E[20;5~'.
key_f34: NULL, '\E[21;5~'.
key_f35: NULL, '\E[23;5~'.
key_f36: NULL, '\E[24;5~'.
key_f37: NULL, '\E[1;6P'.
key_f38: NULL, '\E[1;6Q'.
key_f39: NULL, '\E[1;6R'.
key_f4: '\E[14~', '\EOS'.
key_f40: NULL, '\E[1;6S'.
key_f41: NULL, '\E[15;6~'.
key_f42: NULL, '\E[17;6~'.
key_f43: NULL, '\E[18;6~'.
key_f44: NULL, '\E[19;6~'.
key_f45: NULL, '\E[20;6~'.
key_f46: NULL, '\E[21;6~'.
key_f47: NULL, '\E[23;6~'.
key_f48: NULL, '\E[24;6~'.
key_f49: NULL, '\E[1;3P'.
key_f50: NULL, '\E[1;3Q'.
key_f51: NULL, '\E[1;3R'.
key_f52: NULL, '\E[1;3S'.
key_f53: NULL, '\E[15;3~'.
key_f54: NULL, '\E[17;3~'.
key_f55: NULL, '\E[18;3~'.
key_f56: NULL, '\E[19;3~'.
key_f57: NULL, '\E[20;3~'.
key_f58: NULL, '\E[21;3~'.
key_f59: NULL, '\E[23;3~'.
key_f60: NULL, '\E[24;3~'.
key_f61: NULL, '\E[1;4P'.
key_f62: NULL, '\E[1;4Q'.
key_f63: NULL, '\E[1;4R'.
key_home: '\E[1~', '\EOH'.
key_sdc: NULL, '\E[3;2~'.
key_send: NULL, '\E[1;2F'.
key_sf: '\E[B', '\E[1;2B'.
key_shome: NULL, '\E[1;2H'.
key_sic: NULL, '\E[2;2~'.
key_sleft: NULL, '\E[1;2D'.
key_snext: NULL, '\E[6;2~'.
key_sprevious: NULL, '\E[5;2~'.
key_sr: '\E[A', '\E[1;2A'.
key_sright: NULL, '\E[1;2C'.
key_suspend: '^Z', NULL.
memory_lock: NULL, '\El'.
memory_unlock: NULL, '\Em'.
meta_off: NULL, '\E[?1034l'.
meta_on: NULL, '\E[?1034h'.
newline: '\r\n', NULL.
orig_colors: '\E]R', '\E]104^G'.
parm_ich: NULL, '\E[%p1%d@'.
print_screen: NULL, '\E[i'.
prtr_off: NULL, '\E[4i'.
prtr_on: NULL, '\E[5i'.
repeat_char: NULL, '%p1%c\E[%p2%{1}%-%db'.
reset_1string: NULL, '\Ec\E]104^G'.
reset_2string: '\E<\E["p\E[50;6"p\Ec\E[?3l\E]R\E[?1000l', '\E[\041p\E[?3;4l\E[4l\E>'.
set0_des_seq: '\E[10m', NULL.
set1_des_seq: '\E[11m', NULL.
set2_des_seq: '\E[12m', NULL.
set_attributes: '\E[0%?%p1%p6%|%t;1%;%?%p2%t;4%;%?%p1%p3%|%t;7%;%?%p4%t;5%;m%?%p9%t^N%e^O%;', '%?%p9%t\E(0%e\E(B%;\E[0%?%p6%t;1%;%?%p5%t;2%;%?%p2%t;4%;%?%p1%p3%|%t;7%;%?%p4%t;5%;%?%p7%t;8%;m'.
set_lr_margin: NULL, '\E[?69h\E[%i%p1%d;%p2%ds'.
to_status_line: '\E]0;', NULL.
user8: '\E[?6c', '\E[?%[;0123456789]c'.
Cr: NULL, '\E]112^G'.
Cs: NULL, '\E]12;%p1%s^G'.
Ms: NULL, '\E]52;%p1%s;%p2%s^G'.
Se: NULL, '\E[2 q'.
Ss: NULL, '\E[%p1%d q'.
TS: '\E]0;', NULL.
kDC3: NULL, '\E[3;3~'.
kDC4: NULL, '\E[3;4~'.
kDC5: NULL, '\E[3;5~'.
kDC6: NULL, '\E[3;6~'.
kDC7: NULL, '\E[3;7~'.
kDN: NULL, '\E[1;2B'.
kDN3: NULL, '\E[1;3B'.
kDN4: NULL, '\E[1;4B'.
kDN5: NULL, '\E[1;5B'.
kDN6: NULL, '\E[1;6B'.
kDN7: NULL, '\E[1;7B'.
kEND3: NULL, '\E[1;3F'.
kEND4: NULL, '\E[1;4F'.
kEND5: NULL, '\E[1;5F'.
kEND6: NULL, '\E[1;6F'.
kEND7: NULL, '\E[1;7F'.
kHOM3: NULL, '\E[1;3H'.
kHOM4: NULL, '\E[1;4H'.
kHOM5: NULL, '\E[1;5H'.
kHOM6: NULL, '\E[1;6H'.
kHOM7: NULL, '\E[1;7H'.
kIC3: NULL, '\E[2;3~'.
kIC4: NULL, '\E[2;4~'.
kIC5: NULL, '\E[2;5~'.
kIC6: NULL, '\E[2;6~'.
kIC7: NULL, '\E[2;7~'.
kLFT3: NULL, '\E[1;3D'.
kLFT4: NULL, '\E[1;4D'.
kLFT5: NULL, '\E[1;5D'.
kLFT6: NULL, '\E[1;6D'.
kLFT7: NULL, '\E[1;7D'.
kNXT3: NULL, '\E[6;3~'.
kNXT4: NULL, '\E[6;4~'.
kNXT5: NULL, '\E[6;5~'.
kNXT6: NULL, '\E[6;6~'.
kNXT7: NULL, '\E[6;7~'.
kPRV3: NULL, '\E[5;3~'.
kPRV4: NULL, '\E[5;4~'.
kPRV5: NULL, '\E[5;5~'.
kPRV6: NULL, '\E[5;6~'.
kPRV7: NULL, '\E[5;7~'.
kRIT3: NULL, '\E[1;3C'.
kRIT4: NULL, '\E[1;4C'.
kRIT5: NULL, '\E[1;5C'.
kRIT6: NULL, '\E[1;6C'.
kRIT7: NULL, '\E[1;7C'.
kUP: NULL, '\E[1;2A'.
kUP3: NULL, '\E[1;3A'.
kUP4: NULL, '\E[1;4A'.
kUP5: NULL, '\E[1;5A'.
kUP6: NULL, '\E[1;6A'.
kUP7: NULL, '\E[1;7A'.
ka2: NULL, '\EOx'.
kb1: NULL, '\EOt'.
kb3: NULL, '\EOv'.
kc2: NULL, '\EOr'.
kp5: NULL, '\EOE'.
kpADD: NULL, '\EOk'.
kpCMA: NULL, '\EOl'.
kpDIV: NULL, '\EOo'.
kpDOT: NULL, '\EOn'.
kpMUL: NULL, '\EOj'.
kpSUB: NULL, '\EOm'.
kpZRO: NULL, '\EOp'.
rmxx: NULL, '\E[29m'.
smxx: NULL, '\E[9m'.
For the full dump of the putty-256color entry (with infocmp -x):
# Reconstructed via infocmp from file: /home/chazelas/install/ncurses-6.2-20201107/INSTALL.d/share/terminfo/p/putty-256color
putty-256color|PuTTY 0.58 with xterm 256-colors,
am, bce, bw, hs, mir, msgr, xenl, xon, XT,
colors#0x100, it#8, ncv#22, pairs#0x7fff, U8#1,
acsc=``aaffggjjkkllmmnnooppqqrrssttuuvvwwxxyyzz{{||}}~~,
bel=^G, blink=\E[5m, bold=\E[1m, cbt=\E[Z, civis=\E[?25l,
clear=\E[H\E[J, cnorm=\E[?25h, cr=\r,
csr=\E[%i%p1%d;%p2%dr, cub=\E[%p1%dD, cub1=^H,
cud=\E[%p1%dB, cud1=\ED, cuf=\E[%p1%dC, cuf1=\E[C,
cup=\E[%i%p1%d;%p2%dH, cuu=\E[%p1%dA, cuu1=\EM,
dch=\E[%p1%dP, dch1=\E[P,
dispc=%?%p1%{8}%=%t\E%%G\342\227\230\E%%@%e%p1%{10}%=%t\E%%G\342\227\231\E%%@%e%p1%{12}%=%t\E%%G\342\231\0\E%%@%e%p1%{13}%=%t\E%%G\342\231\252\E%%@%e%p1%{14}%=%t\E%%G\342\231\253\E%%@%e%p1%{15}%=%t\E%%G\342\230\274\E%%@%e%p1%{27}%=%t\E%%G\342\206\220\E%%@%e%p1%{155}%=%t\E%%G\340\202\242\E%%@%e%p1%c%;,
dl=\E[%p1%dM, dl1=\E[M, dsl=\E]0;\007, ech=\E[%p1%dX,
ed=\E[J, el=\E[K, el1=\E[1K, enacs=\E(B\E)0,
flash=\E[?5h$<100/>\E[?5l, fsl=^G, home=\E[H,
hpa=\E[%i%p1%dG, ht=^I, hts=\EH, il=\E[%p1%dL, il1=\E[L,
ind=\n, indn=\E[%p1%dS,
is2=\E7\E[r\E[m\E[?7h\E[?1;4;6l\E[4l\E8\E>\E]R,
ka1=\EOq, ka3=\EOs, kb2=\EOr, kbs=^?, kc1=\EOp, kc3=\EOn,
kcbt=\E[Z, kcub1=\EOD, kcud1=\EOB, kcuf1=\EOC, kcuu1=\EOA,
kdch1=\E[3~, kend=\E[4~, kent=\EOM, kf0=\EOy, kf1=\E[11~,
kf10=\E[21~, kf11=\E[23~, kf12=\E[24~, kf13=\E[25~,
kf14=\E[26~, kf15=\E[28~, kf16=\E[29~, kf17=\E[31~,
kf18=\E[32~, kf19=\E[33~, kf2=\E[12~, kf20=\E[34~,
kf3=\E[13~, kf4=\E[14~, kf5=\E[15~, kf6=\E[17~, kf7=\E[18~,
kf8=\E[19~, kf9=\E[20~, khome=\E[1~, kich1=\E[2~,
kind=\E[B, kmous=\E[<, knp=\E[6~, kpp=\E[5~, kri=\E[A,
kspd=^Z, nel=\r\n, oc=\E]R, op=\E[39;49m, rc=\E8, rev=\E[7m,
ri=\EM, rin=\E[%p1%dT, rmacs=^O, rmam=\E[?7l,
rmcup=\E[2J\E[?47l, rmir=\E[4l, rmkx=\E[?1l\E>,
rmpch=\E[10m, rmso=\E[27m, rmul=\E[24m,
rs2=\E<\E["p\E[50;6"p\Ec\E[?3l\E]R\E[?1000l,
s0ds=\E[10m, s1ds=\E[11m, s2ds=\E[12m, sc=\E7,
setab=\E[%?%p1%{8}%<%t4%p1%d%e%p1%{16}%<%t10%p1%{8}%-%d%e48;5;%p1%d%;m,
setaf=\E[%?%p1%{8}%<%t3%p1%d%e%p1%{16}%<%t9%p1%{8}%-%d%e38;5;%p1%d%;m,
sgr=\E[0%?%p1%p6%|%t;1%;%?%p2%t;4%;%?%p1%p3%|%t;7%;%?%p4%t;5%;m%?%p9%t\016%e\017%;,
sgr0=\E[m\017, smacs=^N, smam=\E[?7h, smcup=\E[?47h,
smir=\E[4h, smkx=\E[?1h\E=, smpch=\E[11m, smso=\E[7m,
smul=\E[4m, tbc=\E[3g, tsl=\E]0;, u6=\E[%i%d;%dR, u7=\E[6n,
u8=\E[?6c, u9=\E[c, vpa=\E[%i%p1%dd, E3=\E[3J, TS=\E]0;,
XM=\E[?1006;1000%?%p1%{1}%=%th%el%;,
xm=\E[<%i%p3%d;%p1%d;%p2%d;%?%p4%tM%em%;,
Note that the entry may change depending on your version of ncurses. For instance between the Ubuntu 20.04 entry (6.2-0ubuntu2 package, 6.2-20200212 upstreams) and the one from 6.2-20201107 above, I see:
$ infocmp -A /usr/share/terminfo -B . putty-256color putty-256color
comparing putty-256color to putty-256color.
comparing booleans.
comparing numbers.
pairs: 65536, 32767.
comparing strings.
kLFT: '\E[D', NULL.
kRIT: '\E[C', NULL.
ka1: NULL, '\EOq'.
ka3: NULL, '\EOs'.
kb2: '\E[G', '\EOr'.
kc1: NULL, '\EOp'.
kc3: NULL, '\EOn'.
kent: NULL, '\EOM'.
kf0: NULL, '\EOy'.
See the changelog inside terminfo.src and the ncurses NEWS file for details.
On the subject of putty vs xterm, further reading:
Note that it's the same person (@ThomasDickey, a prominent contributor here and a reference when it comes to terminals in general) who maintain ncurses and xterm.
